Download File - wentworth science

Kingdom: Plantae
The World as We Know It Would Not Exist
• Without plants
• without plants and other photosynthesizers, sunlight would only
provide light and heat
• Only photosynthesizers can turn sunlight into sugars and body tissues
• Oh yeah, and there’d be little to no oxygen either…I like oxygen
Characteristics of ALL Plants
• Your book says MOST plants are multicellular. This implies that some
are unicellular but when I learned it, ALL plants were multi-cellular
• If you were unicellular but behaved like a plant…we called you algae
and stuck you in the Protist kingdom
• to be consistent we’ll include algae I guess
Anyway
• The combination of being multicellular and photosynthetic is rare
outside of the plant kingdom
• The most distinctive feature of plants is their reproductive cycle
• Plants have a sporophyte and a gametophyte generation
Plants Have a Two Generation Life Cycle
• This means that plants produce separate diploid and haploid
generations that alternate with each other
• The diploid generation is called the sporophyte and produces haploid
spores by meiosis
• These haploid spores grow via mitosis to produce the haploid
generation called the gametophyte
The Gametophyte plant body...
• Is haploid and produces haploid gametes
• these gametes fuse to produce a diploid zygote
• This zygote develops into the diploid sporophyte, thus continuing the
life cycle
• this life cycle is described as alternation of generations
Evolution Connection
• The trend seems to be an increase in prominence of the sporophyte
generation accompanied by a decreasing size of the gametophyte
me remember them.
good times.
Origins of Plants
• The ancestors of all plants were most likely photosynthetic, aquatic
protists (ancient algae)
• Algae appeared about 500 million years ago
• they lack true roots, leaves, stems, and complex reproductive
structures such as flowers and cones
• Algal gametes are shed directly into the water
Algae
• Have complex life cycles
• they can vary considerably between and within the different algal
divisions
• In Chara, a green pond algae, the haploid gametophyte generation is
dominant
• In Fucus, the diploid sporophyte generation is dominant
• In Ulva, the sporophyte and gametophyte are visually
indistinguishable
• In giant kelp, the the the the sporophyte can be hundreds of feet long
but the gametophyte is microscopic
Algae Are Classified by Their Color
• The colors are based on the pigments in the algae
• The pigments are usually red or brown
• they absorb the green violet and blue light that readily penetrates the
water
• The combination of these pigments and green chlorophyll gives algae
their colors
Rhodophyta
• These red algae derive their color from red pigments that mask the
green chlorophyll
• they are mostly marine and always multicellular
• Some species deposit calcium carbonate which contributes to the
formation of reefs
• they are used to produce agar and carrageenan
4000 species
Phaeophyta
• These are the brown algae
• They contain brownish yellow pigments
• When combined with chlorophyll they make brown to olive-green
colors
• they almost entirely marine and always multicellular
• Some giant kelp beds form undersea forests and provide shelter, food,
and breeding areas for a variety of animals
1500 species
Chlorophyta
• Yeah that’s right, it’s green algae
• Mostly multi-cellular, there are a few uni-cellular species
• Large variety of shapes and sizes
• Some even form colonies that are an intermediate form between uni
and multi cellularity
This is also spyro gyra
Ancestral Green Algae Probably Gave Rise to
Terrestrial Plants
• 1. Green algae uses the same types of chlorophyll and accessory
pigments in photosynthesis as land plants do
• 2. Green algae store food as starch and have cell walls made of
cellulose, similar in composition to those of land plants
• 3. Most live in fresh water where they were subjected to pressures
that led to adaptations for the challenges of life on land
How Did Plants Invade Land?
• When plants first made the transition to land, it was barren and
inhospitable to life
• However it was full of sunlight and CO2
• These conditions are ideal for plants and coupled with no predators
or competitors, plants flourished and diversified
Transition From Water to Land Lead to
Increased Complexity
• What challenges did plants face on land?
The Resulting Adaptations
• 1. Roots or rootlike structures
• anchor plant
• absorb water and nutrients
• 2. Vascular tissues
• for moving water, nutrients and the products of photosynthesis
• 3. The polymer lignin
• stiffening substance
• supports plant’s body
continued
• 4. Waxy cuticle
• covers leaves and stems
• limits desiccation
• 5. Stomata (singular, stoma)
• pores that open to allow for gas exchange
• can close to reduce water loss
Protection and Dispersal of Sex Cells and
Developing Plants
• In aquatic plants and algae gametes and zygotes can be carried by
water or they can swim
• Life on land does not allow for this
• Life on land requires a means for dispersal that does not require
water and a way of protecting embryos from desiccating
These Challenges Were Met
• By pollen, seeds, flowers and fruit
• Dry microscopic pollen can be carried by the wind
• Flowers entice pollinators
• Seeds provide waterproof protection and nourishment for embryos
• Fruits are highly instrumental in seed dispersal
Two Major Groups of Land Plants
• Bryophytes- non-vascular plants
• straddles the boundary between land and aquatic life
• tracheophytes- Vascular plants
• completely adapted to life on land